Switched mode voltage converters (switched mode power supplies, SMPS) are widely used for power conversion in automotive, industrial, or consumer electronic applications. A flyback converter is a specific type of switched mode voltage converter, which includes a transformer with a primary winding and a secondary winding that have opposite winding senses. An electronic switch is connected in series with the primary winding, whereas the transformer is magnetized when the electronic switch is closed and demagnetized when the electronic switch is opened. Magnetizing the transformer includes storing energy in the transformer, and demagnetizing the transformer includes transferring the stored energy to the primary winding and a load coupled thereto.
A flyback converter can be operated in a discontinuous conduction mode (DCM). In this operation mode there is a delay time between the time when the transformer has been completely demagnetized and the time when the electronic switch again switches on. During this delay time, parasitic oscillations of a voltage across the electronic switch may occur. In the DCM, the flyback converter may be operated in a quasi-resonant operation mode, in which the electronic switch switches on at those times when the voltage across the electronic switch reaches a minimum. When operating the flyback converter in the quasi-resonant mode the switching frequency of the electronic switch varies, while operating the electronic switch in the flyback converter at a fixed frequency may result in increased switching losses. Nevertheless, there may be scenarios where it is desirable to operate a flyback converter in the DCM at a fixed frequency.